According to a hoop winding embodiment, the reinforcing element is wound around the core while applying a tension. Thus, the reinforcing element wound around the core undergoes a tensile stress, which causes the metal core to undergo a compressive stress. The prestress undergone by the core is similar to the prestress that would be produced by an outside pressure.
Subsea reservoir drilling operations are carried out using a riser pipe allowing the blowout preventer located on the seabed to be connected to the surface. The riser is fitted with at least two auxiliary lines referred to as kill line (KL) and choke line (CL), whose main purpose is to provide a hydraulic connection between the sea surface and the sea bottom. More particularly, auxiliary lines make it possible to supply the well with fluid by circulating below a closed blowout preventer and/or to discharge a fluid from the well, without flowing through the riser pipe that does not withstand high pressures. The fluid thus carried, resulting from a kick from an underground reservoir, can circulate at a pressure that can be above 700 bars.
It has been suggested to use hoop-wound tubes for the auxiliary lines of a riser pipe, notably in patents FR-2,828,262 B1 and FR-2,828,121 B1 filed by the applicant. Manufacturing a high-pressure pipe element from a hoop-wound tube is both simple and economical. FIG. 1 shows an embodiment disclosed in the prior art. The pipe element comprises four distinct parts: a metal tube (1) or core, a first connecting means (3), a second connecting means (4) and hoop layers (2). Tube (1) is first manufactured, from a rolled blank for example, then connecting means (3; 4) are directly welded to ends (8, 9) of tube (1). Hoop winding of the metal assembly is then achieved by winding a reinforcing element around tube (1) and part of connecting means (3, 4), Only the outer parts (33) and (63) of the connecting means are not hooped and they have sufficient thickness to withstand at least the same internal pressure as the hoop-wound part.
Thus, making such a pipe requires connecting means (3; 4) whose ends to be welded have dimensions (diameters and thickness) that are suited to tube (1) so that they can be welded thereto directly. These connecting means (3; 4) have to be mechanically compatible with the stress imposed by hoop winding on transition zones (5) and (7). However, the shapes and the dimensions of the connecting means are also imposed by their operational specifications and by the specific links intended for integration of the safety lines on the riser joint, in particular cooperation with the riser joints. All the constraints relative to the connecting means require a specific and complex implementation of these connecting means.
It is therefore not possible to standardize the design of high-pressure pipe elements according to the prior art (KL and CL) that require connections specific to the riser. The main advantages of the standardization of parts are gain in design and manufacturing time, as well as manufacturing costs reduction.
The present invention aims to use a transition element between the hoop-wound tube and the connecting means so as to allow standardization of the components of the pipe element, such as the hoop-wound tube and the connecting means, while keeping a limited weight, sufficient resistance to internal pressure, and a simple and economical design.